1. Field of the Invention
The present invention relates to an oligonucleotide primer set for amplifying at least one target sequence of the cagA gene of Helicobacter pylori (H. pylori), a method of detecting H. pylori using the primer set, and a kit for detecting H. pylori, including the primer set.
2. Description of the Related Art
Helicobacter pylori (H. pylori) (formerly known as Campylobacter pylori) is a gram-negative bacterium that colonizes human gastric mucosa. H. pylori is frequently detected from gastric biopsy samples derived from patients suffering from gastritis and gastric ulcers. Epidemiological studies have shown that H. pylori is a causative substance for gastritis, gastric ulcers, and duodenal ulcers and is associated with diseases such as stomach cancer.
Once it colonizes gastric mucosa, H. pylori survives in the stomach and cannot be eradicated without medical treatment. Colonization of the gastric mucosa with H. pylori leads to type B chronic gastritis. H. pylori infection is responsible for 85% of chronic gastritis cases.
The infection route of H. pylori has not yet been firmly established, but it has been reported that H. pylori infection occurs when water or food in the vomit and feces of infected people is ingested through the mouths of other people or when the vomit and feces of infected people spread from person to person via flies. It has also been reported that H. pylori directly spreads from person to person through the oral-oral route. It has been reported that 50% or more of the Korean population are infected with H. pylori, and the infection rate rapidly increases with age (although it varies according to regional areas or occupation): 50-60% in adults, 1.1% in children aged under 5 years, 12.8% in children aged 5-9 years, and 20.4% in children aged 10-14 years.
When humans are infected with H. pylori, various upper gastrointestinal lesions can be caused according to the diversity of the H. pylori strains and the sensitivity of the infected humans. Most people infected with H. pylori do not show any symptoms immediately after infection but develop symptoms gradually.
In this regard, early diagnosis of H. pylori infection is very important in prevention or treatment of various gastric diseases. For this, it is necessary to rapidly and reproducibly detect even a small quantity of gene products produced by H. pylori at an initial stage of H. pylori infection.
U.S. Patent Publication No. 2003/0175746 discloses a method of detecting H. pylori in a biological sample and its related primers. U.S. Patent Publication No. 2006/0003350 discloses a method of detecting H. pylori in a biological sample, a diagnostic kit, and their related primers.
According to a conventional method of detecting H. pylori, mucosal biopsy samples are collected and cultured. However, problems arise in that H. pylori is irregularly distributed in the gastric surface mucosa, it is difficult to collect mucosal biopsy samples, and isolated epithelial cells from infected people are not efficiently cultured. Saliva samples can also be used for the detection of H. pylori. It has been demonstrated that the sensitivity of diagnosis of H. pylori infection using saliva samples is comparable to that of conventional diagnosis of H. pylori infection using other standard samples. However, H. pylori coexists with several hundreds of kinds of oral flora in saliva. Thus, in order to use a nucleic acid detection method, it is necessary to develop a marker capable of discriminating H. pylori from other oral flora.
While searching for a method of detecting H. pylori based on the above-described conventional techniques, the present inventors found that H. pylori can be specifically detected in saliva containing H. pylori and other oral flora using a primer set capable of amplifying at least one target sequence of the cagA gene of H. pylori, and thus, completed the present invention.